Seal construction for a mold structure for encapsulating glass with a gasket

ABSTRACT

A unique dynamic seal assembly is used in a mold structure for encapsulating a glass window assembly with a gasket. The seal assembly resiliently supports the window assembly and cooperates with the mold structure for defining a gasket forming cavity. The mold structure typically includes two cooperating mold sections, each of which can be provided with a groove for receiving a separate dynamic seal assembly. Each seal assembly includes a first sealing body having a sealing surface which faces and is adapted to sealingly contact the window assembly. The first seal element is formed of a non-deformable, non-compressible material and is connected to a second seal element formed of a deformable, non-compressible material which is responsive to pressure applied to the first seal element for adjusting the position of the first seal element in the mold to accommodate thickness variations in a window assembly contacting the first surface. The first seal element is typically formed of a Teflon material and is movable in a vertical direction to accommodate thickness variations in a window assembly contacting the first sealing surface. The second seal element is formed of a silicon rubber material or is a tube filled with a non-compressible fluid.

This is a division of application Ser. No. 07/088,123 filed Aug. 21,1987, now U.S. Pat. No. 4,854,599 issued Aug. 8, 1989.

BACKGROUND OF THE INVENTION

The present invention relates to a seal assembly for use in an injectionmolding process and; more particularly, to a seal assembly for use in amold for making encapsulated window structures.

Initially, fixed window assemblies for vehicles were comprised of aplurality of elements including adhesive sealants applied around themarginal edges of a glass sheet, suitable mechanical fasteners such asmetal clips, and exterior decorative trim strips disposed to cover thejunction between the marginal edges of the glass sheet and the adjacentportions of the vehicle frame. Such window structures were costly,especially from a labor standpoint, since it was necessary to assemblethe individual elements along the vehicle assembly line.

Subsequently, in an endeavor to improve the above window structure,unitary window assemblies of the type illustrated in U.S. Pat. No.4,072,340 were developed. These window assemblies included a sheet ofglass, an adjacent frame, and a casing or gasket of molded material,such as polyvinylchloride, extending between the frame and theperipheral edge of the window to hold the sheet of glass and the frametogether. Fasteners were provided at spaced locations along the framesuch that the entire assembly could be guided into a location over theopening in a vehicle body as a unit. Other types of unitary windowassemblies are disclosed in U. S. Pat. Nos. 3,759,004 and 4,364,595.While such unitary window structures greatly reduce the time required tomount the window assembly in an associated vehicle, such structures arerelatively costly, since the individual components required to produceeach window assembly generally must be manually assembled.

Recently, window assemblies have been formed by encapsulating at least aportion of the periphery of a sheet of glass with a gasket material.Typically, the gasket is formed by curing a polymeric gasket-formingmaterial in situ on the glass sheet to encapsulate a predeterminedportion of the marginal edge of the sheet. The gasket can bepolyurethane and formed, for example, by a reaction injection moldingprocess.

A mold structure which can be utilized to encapsulate a glass sheet withan integrally molded gasket is disclosed in U.S. Pat. No. 4,561,625issued to W. R. Weaver and assigned to the assignee of the presentinvention. In this patent, the mold structure includes at least two moldsections having facing surfaces cooperating to define a chamber forreceiving a glass sheet. A resilient seal means is positioned in atleast one of the mold sections about at least a portion of the peripheryof the chamber and functions to resiliently support the glass sheetwithin the chamber. Each mold section includes a metallic main bodyportion, and the seal means maintains at least the portion of the glasssheet located inwardly of the seal means in spaced-apart relationshipwith the metallic main body portions of the mold sections.

Also, in the Weaver patent, the seal means cooperates with predeterminedportions of the glass sheet and the mold sections for defining a gasketforming cavity having a configuration corresponding to the gasket to beformed on the glass sheet. At least a portion of the facing surfaces ofthe mold sections disposed outwardly of the gasket forming cavity are inmetal-to-metal contact with one another. This enables the amount theseal means is compressed and the dimensions of the gasket to becontrolled.

The prior art seals are typically deformable, static silicone rubber orTeflon coated elastomeric seals. In order to accommodate differences incontour or edge profile which occur between individual glass sheets,these seals must be deformed sufficiently to fill "low spots" andprevent gaps between the glass and the seal which would cause excessiveflash formation on the gasket being molded. This deformation causes veryhigh pressure on the high spots, resulting in seal fatigue and leadingto premature seal failure. In some instances, the excessive pressure maycause breakage of the glass sheet. In all cases excess pressure distortsthe seal contour resulting in distorted molded gasket shapes.

SUMMARY OF THE INVENTION

The present invention relates to a unique seal assembly for a moldstructure for molding a gasket in situ around the periphery of a glasswindow assembly. The seal assembly is adapted to resiliently support thewindow assembly within the mold structure and cooperates with the moldstructure for defining a gasket forming cavity. One seal structure ofthe present invention is dynamic and includes a deformable seal elementwhich automatically compensates for pressure differentials caused by lowand high spots in the sheet of glass. With the present invention,excessive pressure generated at a high spot on the glass is transferredto an adjacent low spot to equalize the pressure along the whole lengthof the seal.

More specifically, the mold structure typically includes two cooperatingmold sections, each of which can be provided with a groove for receivinga separate dynamic seal assembly. Each seal assembly can be of thedynamic type or one of the seal assemblies can be a static type. Thedynamic type seal includes a first seal element formed of anon-deformable, non-compressible material having a first surface adaptedto sealingly contact a window assembly. The seal assembly also includesa second seal element formed of deformable, non-compressible materialand connected to the first seal element and responsive to pressureapplied to the first seal element for adjusting the position of thefirst seal element in a mold to accommodate thickness variations in awindow assembly contacting the first surface.

In one embodiment, the second seal element is formed of a rubbermaterial having a durometer hardness of approximately seventy. Inanother embodiment, the second seal element is a fluid filled bladderpositioned between the first seal element and the cooperating moldsection. In either case, when increased pressure is applied to a localarea of the seal as a result of a contour difference between the sealand the window assembly, the second seal element deforms toautomatically transfer at least a portion of the applied pressure toadjacent areas of the seal. Such a seal construction produces a moreeffective seal and reduces seal fatigue, thereby increasing the life ofthe seal, and assures molding an undistorted, true to design, moldedgasket. The first seal element can be formed of a non-deformable,non-compressible material such as a Teflon material having a durometerhardness of approximately ninety.

It is accordingly an object of the invention to produce an encapsulationseal useful in the production of flash-free plastic materialencapsulated products. The resultant seal structure may besatisfactorily utilized in the production of encapsulated glass sheetproducts to provide the desired flash-free product without subjectingthe glass assembly to excessive stresses which might otherwise causebreakage of the glass.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as other advantages of the present invention, willbecome readily apparent to those skilled in the art from the followingdetailed description of the preferred embodiments when considered in thelight of the accompanying drawings, in which:

FIG. 1 is a fragmentary sectional view of a prior art window assemblyand mold structure;

FIG. 2 is a fragmentary elevational view of the prior art windowassembly and seal of FIG. 1;

FIG. 3 is a fragmentary sectional view of a window assembly and moldstructure incorporating a seal assembly in accordance with the presentinvention;

FIG. 4 is a fragmentary sectional view of an alternate embodiment of theseal assembly shown in FIG. 3;

FIG. 5 is an enlarged, exploded view of the upper seal body shown inFIG. 4;

FIG. 6 is a fragmentary sectional view of a second alternate embodimentof the seal assembly shown in FIG. 3;

FIG. 7 is an enlarged, exploded view of the upper seal body shown inFIG. 6;

FIG. 8 is a fragmentary sectional view of a third alternate embodimentof the seal assembly shown in FIG. 3;

FIG. 9 is an enlarged, exploded view of the upper seal body shown inFIG. 8;

FIG. 10 is a fragmentary sectional view of a fourth alternate embodimentof the seal assembly shown in FIG. 3; and

FIG. 11 is a fragmentary sectional view of an alternate embodiment ofthe lower seal assembly shown in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT

There is shown in FIG. 1 a window assembly 10 positioned within a moldstructure 11 utilizing a seal according to a prior art mold structure ofthe type disclosed in above-mentioned U.S. Pat. No. 4,561,625, which isherein incorporated by reference. The mold structure 11 includes a lowersection 12 and an upper section 13 which are coupled to suitable means(not shown) for opening and closing the mold sections 12 and 13. Themold structures 12 and 13 are typically formed of a rigid material suchas, for example, steel or aluminum. Also, each of the mold sections 12and 13 can be provided with passageways (not shown) for circulating asuitable coolant or heating fluid through the

The mold sections 12 and 13 are provided with recessed portions 14 and15 respectively in facing relationship to one another such that, whenthe mold sections are closed, the recessed portions 14 and 15 cooperateto define a sheet receiving or glass clearance chamber for receiving thewindow assembly 10 on which a gasket is to be formed. When the moldsections are open, the window assembly 10 is positioned on the lowersection 12 so that the outer peripheral portion of the lower surface ofthe glass rests on a resilient lower seal 16 positioned within a groove17 formed in the upper surface of the lower section 12. After the windowassembly 10 is suitably positioned on the seal 16 of the lower moldsection 12, the upper mold section 13 is lowered into position to enablethe outer peripheral portions of the facing surfaces 18 and 19 of thecooperating mold sections 12 and 13 respectively to be clamped inmetal-to-metal contact, as shown in FIG. 1. The upper mold section 13carries a resilient upper seal 20 positioned in a groove 21 formedopposite the groove 17. The upper seal 20 cooperates with the lower seal16 to press yieldingly against the glass sheet window assembly 10 andresiliently support the window assembly within the glass clearancechamber.

The chamber or space between the surfaces of the recessed portions 14and 15 is slightly larger than the thickness of the window assembly 10.However, it will be appreciated that the glass clearance chamber can beformed of any shape as long as the chamber is sufficiently large toavoid any glass-to-metal contact between the glass sheets of the windowassembly 10 and the metallic mold sections 12 and 13. For example, theportions of the mold sections 12 and 13 which are below and aboverespectively the central portion of the glass sheet window assembly 10can be removed such that each mold section will be generallyring-shaped. The seals 16 and 20 are preferably formed of a siliconerubber material and secured within the respective grooves 17 and 21 bymeans of a suitable adhesive.

In addition to resiliently supporting the window assembly 10 within theglass clearance chamber, the seals 16 and 20 cooperate with selectedportions of the window assembly 10 and the mold sections 12 and 13 fordefining a gasket forming cavity utilized to form a gasket 22 about theperipheral edge of the window assembly 10. More specifically, in FIG. 1,the gasket forming cavity is defined by the cooperation of a lowergasket shaping surface 23 of the lower mold section 12, an upper gasketshaping surface 24 of the upper mold section 13, portions 16a and 20a ofthe seals 16 and 20 respectively, and the peripheral edge portion of thewindow assembly 10. The gasket forming cavity can be constructed to formthe gasket 22 on either the entire periphery of the window assembly 10,or on a selected peripheral portion. Once the mold sections are closed,a flowable polymeric gasket forming material can be injected into thecavity through suitable inlet means (not shown).

Referring to FIG. 2, there is show an elevational view of a portion ofthe window assembly 10 and the lower seal 16. While the seal 16 ideallyconstructed with a contour which conforms to the contour of the edge ofthe window assembly 10, due to the normal glass forming and bendingoperations, the window assembly often has a contour which is slightlydifferent from the contour of the seal 16. In FIG. 2, there is shown at25 a difference in contour between a peripheral edge portion of thewindow assembly 10 and an upwardly facing portion of the seal 16. Thelower surface of the window assembly 10 in the area 25 is spacedupwardly from the seal 16 when the window assembly is placed in theupper surface of the seal 16. The contour difference 25 forms a space orgap 26 which, prior to the injection of the gasket forming material,must be sealed in order to prevent leakage of the gasket formingmaterial past the seal 16, thereby producing undesirable flash on thefinished gasket.

When the upper mold section is placed on the top of the window assembly10, pressure is applied in the direction of the arrow 27. The gasket 16will tend to deform by compressing in the regions on either side of thegap 26 and, if enough pressure is applied, the region of the gasket 16adjacent the contour difference area 25 will contact the facing surfaceof the window assembly 10 to eliminate the gap 26. However, when suchcontact occurs, relatively little pressure is applied to the seal 16 bythe area 25 of the window assembly 10, thereby increasing thepossibility of a blowout which will allow leakage of the gasket formingmaterial and prevent fill-out resulting in an incomplete gasket. Inaddition, the regions of the seal 16 on either side of the gap 26 aresubjected to increased pressure which causes increased seal fatigue andresults in premature seal failure. Further, if the increased pressure isexcessive, breakage of the window assembly can occur.

There is shown in FIG. 3 a seal assembly according to the presentinvention. A window assembly 30, similar to the window assembly 10, ispositioned in a mold 31 having a lower section 32 and an upper section33. The mold sections 32 and 33 are typically formed of a metallicmaterial and have recessed portions 34 and 35 respectively to form achamber for receiving the window assembly 30 and preventingglass-to-metal contact between the window assembly and the moldsections. A stationary lower seal body 36, constructed of anon-deformable, non-compressible material such as Teflon material havinga ninety durometer hardness, is positioned in a groove 37 and has asealing surface 38 which engages a lower surface of the window assembly30 to support the window assembly above the lower section 32. The groove37 has an upwardly facing bottom wall 39 upon which the seal 36 restsand a side wall 40 against which the seal 36 is retained by a clamp 41.The clamp 41 can be retained in the groove 37 by any suitable fastenermeans.

An upper seal body 42 is constructed of three sections and is located ina groove 43 formed in the upper section 33 and has a sealing surfacewhich engages the window assembly 30. The upper seal 42 is retained inthe groove 43 by a clamp 44 which in turn can be retained in the groove43 by any suitable fastener means. The lower section 32 and the uppersection 33 have a lower cavity 45 and an upper cavity 46 respectivelyformed therein for forming a gasket which is similar to the gasket 24 inFIG. 1.

The upper seal body 42 includes an outer section 47, a center section48, and an inner section 49. The outer section 47 and the center section48 can be formed of a non-deformable, non-compressible material such asTeflon material having a ninety durometer hardness. The inner section 49can be formed of a deformable, non-compressible material such assilicone rubber having a seventy durometer hardness. The outer section47 is similar in shape to the lower seal body 36 and abuts a side wall50 of the groove 43 formed in the upper mold section 33. The outersection 47 also rests against a bottom wall 51 of the groove 43 and isof such a length that it does not extend out of the groove 43 and intothe upper cavity 46.

The center section 48 includes a sealing surface 52 which engages anupper surface of the window assembly 30. A V-shaped groove 53 is formedin a side wall of the center section 48 abutting the inner section 49and adjacent the end of the center section 48 opposite the sealingsurface 52. The center section 48 is spaced from the bottom wall 51 ofthe groove 43 and the sealing surface 52 extends beyond the adjacent endof the outer section 47.

One end of the inner section 49 is formed with a generally planarsurface 54 which abuts the bottom wall 51 of the groove 43. A side wallof the inner section 49 abutting the center section 48 extends into thegroove 53 and partially covers the end of the center section 48 adjacentthe groove 53 leaving a gap 55 between the outer section 47 and theinner section 49. The opposite side wall of the inner section 49includes a first planar surface 56 abutting a surface of the clamp 44. Asecond planar surface 57 of the side wall extends from the planarsurface 54 to an intersection with an edge of the planar surface 56. Thesurfaces 56 and 57 are formed at an angle with respect to the verticalsuch that the side wall defined by these surfaces extends outwardly. Theinner section 49 also has an outwardly extending sealing surface enddefined by a pair of planar surfaces 58 and 59. The planar surface 58intersects the planar surface 56 along one edge and intersects theplanar surface 59 along an opposite edge. The planar surface 59intersects the side wall of the inner section 49 which abuts the centersection 48.

When the lower mold section 32 and the upper mold section 33 are closedtogether such that a facing surface 60 of the lower section 32 contactsa facing surface 61 of the upper section 33, the sealing surface 38 ofthe lower seal body 36 will contact the lower surface of the windowassembly 30. The lower seal body 36 will prevent gasket forming materialin the lower cavity 45 from entering the groove 37 and the recessedportion 34 of the lower mold section 32 thereby preventing the formationof flash.

At the same time, the sealing surface 52 of the center section 48 willcontact the upper surface of the window assembly 30 to prevent gasketforming material in the upper cavity 46 from entering the groove 43 andthe recessed portion 35 of the upper mold section 33. However, since thethickness of the window assembly 30 will vary from unit to unit, thecenter section 48 will accommodate such variations in a generallyvertical direction by sliding against the outer section 47 whiledeforming the inner section 49 as required. The section 47 also providesa glass contacting surface to accommodate misaligned or oversizedsheets. The length of sheets can vary due to variations in curvaturefrom one sheet to another. Thus, the lower seal body 36 functions as astatic seal while the upper seal body 42 functions as a dynamic seal. Insome applications, it may be desirable to eliminate the outer section 47such as where the upper seal body 42 will abut an insert to be moldedinto the gasket. Also, the outer section 47 could be utilized betweenthe lower seal body 36 and the side wall 40 in the lower mold section 32as a spacer.

An alternate embodiment of the seal assembly in accordance with thepresent invention is shown in FIG. 4. Like reference numerals designatesimilar elements. The window assembly 30 is positioned in the mold 31wherein the lower mold section 32 and the upper mold section 33 havebeen closed together. A peripheral portion of the lower surface of thewindow assembly 30 rests on the lower seal body 36 which is positionedin the lower mold section 32 by the clamp 41. Similarly, an upper sealbody 70 is retained in the upper mold section 33 by the clamp 44. Thelower seal body 36 is formed of a non-deformable, non-compressiblematerial such as a Teflon material and functions as a static seal. Theupper seal body 70 is of two piece construction and functions as adynamic seal.

The seal 70 is shown in more detail in an enlarged, exploded view FIG.5. An outer section 71 includes a generally vertically extending leg 72connected at a lower end thereof to a right end of a generallyhorizontally extending leg 73, the legs extending generally at rightangles to one another. The leg 72 is adapted to abut the side wall 50 ofthe groove 43 formed in the upper mold section 33. The leg 73 is adaptedto contact the upper surface of the window assembly 30. Thus, adownwardly facing surface 74 of the leg 73 functions as the sealingsurface 52 of the upper seal body 42 shown in FIG. 3. Typically, theouter section 71 is formed of Teflon material and the legs 72 and 73 areof a thickness, typically 0.060 inches, which permits some degree offlexing.

The upper seal body 70 also includes an inner section 75 which issimilar to the inner section 49 shown in FIG. 3. The inner section 75includes an upwardly facing generally horizontally extending planarsurface 76 which is adapted to abut the bottom wall 51 of the groove 43.A generally vertically extending planar side wall 77 intersects one edgeof the planar surface 76. The side wall 77 is adapted to abut an innerplanar surface 78 of the leg 72 formed on the outer section 71. Oppositethe side wall 77 is a generally outwardly extending side wall formed ofplanar surfaces 79 and 80. The planar surface 79 extends betweenadjacent edges of the planar surface 76 and the planar surface 80. Theplanar surface 80 is generally parallel to and abuts a facing surface ofthe clamp 44.

The downwardly facing side of the inner section 75 is formed from threeplanar surfaces 81, 82 and 83. The surface 81 extends between opposededges of planar surface 80 and planar surface 82. The planar surfaces 81and 82 are angled downwardly to form a generally outwardly extendingsurface. The planar surface 83 extends generally horizontally betweenopposed edges of the side wall 77 and the planar surface 82. The innersection 75 can be formed of a silicone rubber material having a seventydurometer hardness. Thus, the inner section 75 is deformable andnon-compressible. When the mold sections 32 and 33 are moved together,the inner section 75 permits the leg 73 of the outer section 71 to flexthereby accommodating any variations in the thickness of the windowassembly 30.

There is shown in FIG. 6 a second alternate embodiment of the sealassembly in accordance with the present invention. As in FIG. 4, likereference numerals are utilized to designate like elements from FIG. 3.An upper seal body 90 is retained in the groove 43 formed in the uppermold section 33 by a clamp 91. The upper seal body 90 and the clamp 91are shown in more detail in an enlarged, exploded view FIG. 7. The upperseal body 90 includes an outer section 92, an inner section 93, and acover section 94. The outer section 92 is generally U-shaped having afirst vertically extending leg 95 adapted to abut the side wall 50 ofthe groove 43 and a second generally vertically extending leg 96 adaptedto abut the clamp 91. The clamp 91 has a pair of steps 97 and 98 formedon the surface facing the leg 96. The lower step 98 accepts a flange 99formed on the upper end of the leg 96 and extending toward the clamp 91.The step 98 limits the downward movement of the leg 96. The bottom endsof the legs 95 and 96 are joined by a generally horizontally extendingmember 100 having a downwardly facing sealing surface 101 formed thereonfor contacting the upwardly facing surface of the window assembly 30.The outer section 92 can be formed of a non-deformable, non-compressiblematerial such as Teflon and the legs 95 and 96 and 100 can be of athickness such that they will flex under pressure.

The inner section 93 has a downwardly facing generally horizontallyextending surface 102 which abuts the upper surface of the horizontalmember 100. Extending generally vertically upward from one edge of thesurface 102 is a generally planar side wall 103 which abuts an innersurface of the leg 96. Opposite the side wall 103 is a side wall 104which tapers inwardly from an edge of the surface 102. The upper edgesof the side walls 103 and 104 are connected by three generally planarsurfaces 105, 106 and 107. The surface 106 is generally horizontallyextending and is connected at opposite edges to the surfaces 105 and107. The surface 105 extends between adjacent edges of the side wall 103and the surface 106 and the surface 107 extends between adjacent edgesof the side wall 104 and the surface 106. The inner section 93 can beformed of a silicone rubber material.

The cover section 94 is formed of a generally horizontally extending leg108 and a generally vertically extending leg 109 to form a generallyL-shaped body. An inwardly facing surface of the leg 109 is tapered atan angle to match the taper of the side wall 104 of the inner section93. Thus, the leg 109 functions as a wedge between the leg 95 of theouter section 92 and the side wall 104 of the inner section 93 to forcethe inner section 93 against the leg 96 of the outer section 92. Athicker section of the leg 108 adjacent the leg 109 has a downwardlyfacing surface 110 which abuts the planar surface 106 of the innersection 93. A thinner section of the leg 108 has a downwardly facingsurface 111 which rests on the upper step 97 of the clamp 91. When theflange 99 abuts the lower step 98, there is a gap 112 formed between theupper surface of the flange 99 and the downwardly facing surface 111.Thus, when the lower mold section 32 and the upper mold section 33 aremoved together, the horizontal member 100 is free to flex moving the leg96 and the flange 99 in a generally vertical direction in the gap 112 toaccommodate any variations in the thickness of the window assembly 30.

There is shown in FIG. 8 a third alternate embodiment of the sealassembly in accordance with the present invention. Like referencenumerals designate similar elements. An upper seal body 120 is retainedin the groove 43 in the upper mold section 33 by a clamp 121. The upperseal body and the clamp 121 are shown in more detail in an exploded,enlarged view FIG. 9. The upper seal body 120 includes an outer section122 for retaining an inflatable tube 123 and a cover section or cap 124.The outer section 122 is formed of a Teflon material and is generallyU-shaped and symmetrical. A pair of generally vertically extending legs125 are joined at their lower ends by a generally horizontally extendingmember 126. Each of the legs 125 has an outwardly extending flange 127formed at its upper end. The clamp 121 has a step 128 formed in the sidewall which abuts the outer section 122. The distance between the step128 and a bottom wall 51 of the groove 43 is greater than the height ofthe flange 127 such that a gap 129 is formed. The upper mold section 33is modified by forming a groove 130 in the side wall 50 of the sealretaining groove 43. The width of the groove 130 is greater than theheight of the flange 127 such that a gap 131 is formed when one of theflanges 127 is inserted into the groove 130.

The tube 123 is positioned in the outer section 122 and the gap betweenthe upper ends of the legs 125 is closed by the cap 124. The tube 123 isinflated with a fluid such that the outer surface of the tube 123contacts the inner surfaces of the legs 125, the horizontal member 126and the cap 124. When the lower mold section 32 and the upper moldsection 33 are closed together, a downwardly facing sealing surface 132of the member 126 contacts the upwardly facing surface of the windowassembly 30. The outer section 222 is free to move in a verticaldirection thereby deforming the tube 123 to compensate for anyvariations in the thickness of the window assembly 30. The tube istypically formed of a silicone rubber material.

There is shown in FIG. 10 a fourth alternate embodiment of the sealassembly according to the present invention. All of the elements shownin FIG. 10 are similar to like-numbered elements in the seal assemblyshown in FIG. 6 with the exception that the inner section 93 of theupper seal body 90 in FIG. 6 has been replaced with an inflatable tube135 similar to the inflatable tube 123 shown in FIG. 8. Thus, the outersection 92 flexes by deforming the inflated tube 135 to accommodatevariations in the thickness of the window assembly 30.

FIG. 11 is a sectional view of an alternate embodiment of the lower sealassembly shown in FIG. 3. The lower mold section 32 has the groove 37formed therein for receiving a lower seal assembly 140. The sealassembly 140 includes a first seal body 141 and a second seal body 142.The groove 37 includes the upwardly facing bottom wall 39 upon which theseal body 142 rests. The seal body 142 is generally L-shaped with agenerally horizontally extending leg 143 joined to a generallyvertically extending leg 144. The leg 143 abuts the bottom wall 39 andthe leg 142 abuts the clamp 41. The groove 37 also has the side wall 40against which the seal body 141 is retained by the leg 144 and the clamp41. The seal bodies 141 and 142 provide approximately twice the surfacearea with sealing surfaces 145 and 146 respectively as the lower sealbody 36 with sealing surface 38 in FIG. 3. Thus, the sealing load isdistributed over a larger area to reduce the rate of flattening andfrequency of replacement of the seal bodies. Typically the seal body 141is formed of Teflon material and the seal body 142 is formed of aurethane material having a ninety durometer hardness.

Typically, the upper and lower seals extend around those portions of thewindow periphery to which the gasket is to be molded. If the gasket isto be formed around the entire periphery of the window assembly, theupper and lower seals in the mold will be formed as rings. Where theseal assembly includes an inflatable tube, a relatively non-compressibleliquid such as oil could be utilized to fill the tube. If a compressiblegas is utilized instead, a pressure fluid source at a relatively higherpressure could be utilized and include a pressure regulator which couldbe set to provide the desired pressure to the tube. Should the molds andseals have a tendency to pose too high a pressure on the tubes, acompensator can be provided.

In accordance with the provisions of the patent statutes, the principleand mode of operation of the present invention have been described inwhat has been considered to represent the preferred embodiment. However,it should be understood that the invention may be practiced otherwisethan as specifically illustrated and described without departing fromthe scope of the attached claims.

What is claimed is:
 1. A seal assembly for a mold for encapsulating awindow assembly, comprising:a first seal element formed of anon-deformable, non-compressible material and having a first surfaceadapted to sealingly contact a window assembly and a second surface; anda second seal element formed of a deformable, non-compressible materialand having a first surface abutting said second surface of said firstseal element and responsive to pressure applied to said first sealelement for adjusting the position of said first seal element in a moldto accommodate thickness variations in a window assembly contacting saidfirst surface, said first seal element being generally L-shaped withsaid first surface thereof being an outer surface of one of its legs andsaid second surface being an inner surface of the other one of its legs.2. The seal assembly according to claim 1, including clamp means forretaining said first seal element and said second seal element in agroove formed in a mold.
 3. A mold structure for forming a gasket on apredetermined portion of a frangible sheet, comprising:at least twocooperating mold sections having facing surfaces defining a chamber forreceiving the sheet; a seal assembly positioned in at least one of thefacing surfaces of said mold sections to assist in supporting the sheetwithin the sheet receiving chamber and to cooperate with thepredetermined portion of the sheet to at least in part define a gasketforming cavity corresponding to the gasket to be formed on the sheet;said seal assembly including a first seal element formed of anon-deformable, non-compressible material and having a first surfaceadapted to sealingly contact a window assembly and a second surface; asecond seal element formed of a deformable, non-compressible materialand having a first surface abutting said second surface of said firstseal element and responsive to pressure applied to said first sealelement for adjusting the position of said first seal element in said atleast one of the facing surfaces of the mold sections to accommodatethickness variations in the window assembly contacting said firstsurface of the first seal element, said first seal element beinggenerally L-shaped with said first surface thereof being an outersurface of one of its legs and said second surface being an innersurface of the other one of its legs; and inlet means for introducing aflowable gasket material into the gasket forming cavity.
 4. A moldstructure according to claim 3, wherein the first seal element has aDurometer hardness of about
 90. 5. A mold structure according to claim3, wherein the second seal element has a Durometer hardness of about 70.6. A mold structure according to claim 3, wherein the first seal elementis formed of a polytetrafluoroethylene material.
 7. A mold structureaccording to claim 3, wherein the second seal element is formed of asilicone rubber material.
 8. A mold structure according to claim 3,wherein said first seal element is formed of a polytetrafluoroethylenematerial having a Durometer hardness of about 90, and said second sealelement is formed of a silicone rubber material and has a Durometerhardness of about
 70. 9. A mold structure according to claim 3,including clamp means for retaining said seal assembly in a grooveformed in said at least one of the facing surfaces of the mold sections.10. A mold structure according to claim 8, including clamp means forretaining said seal assembly in a groove formed in said at least one ofthe facing surfaces of the mold sections.